feat: add look_at tool and multimodal-looker agent

Add a new tool and agent for analyzing media files (PDFs, images, diagrams)
that require visual interpretation beyond raw text.

- Add `multimodal-looker` agent using Gemini 2.5 Flash model
- Add `look_at` tool that spawns multimodal-looker sessions
- Restrict multimodal-looker from calling task/call_omo_agent/look_at tools

Inspired by Sourcegraph Ampcode's look_at tool design.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/agents/multimodal-looker.ts

@@ -0,0 +1,42 @@
+import type { AgentConfig } from "@opencode-ai/sdk"
+
+export const multimodalLookerAgent: AgentConfig = {
+  description:
+    "Analyze media files (PDFs, images, diagrams) that require interpretation beyond raw text. Extracts specific information or summaries from documents, describes visual content. Use when you need analyzed/extracted data rather than literal file contents.",
+  mode: "subagent",
+  model: "google/gemini-2.5-flash",
+  temperature: 0.1,
+  tools: { Read: true },
+  prompt: `You interpret media files that cannot be read as plain text.
+
+Your job: examine the attached file and extract ONLY what was requested.
+
+When to use you:
+- Media files the Read tool cannot interpret
+- Extracting specific information or summaries from documents
+- Describing visual content in images or diagrams
+- When analyzed/extracted data is needed, not raw file contents
+
+When NOT to use you:
+- Source code or plain text files needing exact contents (use Read)
+- Files that need editing afterward (need literal content from Read)
+- Simple file reading where no interpretation is needed
+
+How you work:
+1. Receive a file path and a goal describing what to extract
+2. Read and analyze the file deeply
+3. Return ONLY the relevant extracted information
+4. The main agent never processes the raw file - you save context tokens
+
+For PDFs: extract text, structure, tables, data from specific sections
+For images: describe layouts, UI elements, text, diagrams, charts
+For diagrams: explain relationships, flows, architecture depicted
+
+Response rules:
+- Return extracted information directly, no preamble
+- If info not found, state clearly what's missing
+- Match the language of the request
+- Be thorough on the goal, concise on everything else
+
+Your output goes straight to the main agent for continued work.`,
+}